The present invention relates to solar evaporators for thermal engines and, more particularly, to solar evaporators for Stirling engines in which temperatures in different parts of the evaporator tend to be equalized.
Evaporators for thermal or Stirling engines are utilized to heat a medium, ranging from cryogenic gases such as hydrogen to liquid metals such as sodium, and transport and medium from an evaporator to a condenser to provide energy to run the engine. Various types of evaporators and condensers exist in the art. One type, illustrated in U.S. Pat. No. 4,523,636, assigned to the assignee of the present invention, the specification of which is herein incorporated by reference, illustrates a heat fin configuration coupled with a heat pipe to transport the medium from the evaporator to the condenser.
The above art generally requires an external heat source such as heated air or the like to heat the fins to vaporize the medium and cause it to flow through the heat pipe. The present invention enables solar energy to heat the evaporator to in turn heat the medium and cause it to flow between the evaporator and the condenser. Devices which utilize solar energy to heat evaporators for thermal or Stirling engines are illustrated in U.S. patent application No. 019,651, filed Feb. 27, 1987, entitled "Solar Powered Stirling Engine", assigned to the assignee of the present invention, the specification of which is herein incorporated by reference. It is desirable to maximize the solar energy to heat the evaporator to transport the heated medium and to reduce problems resulting from unequal temperatures in spaced parts of the evaporator due to uneven distribution of solar heat on the receiving face of the evaporator.
Accordingly, the present invention provides a solar evaporator which enables the medium to be heated to substantially even temperatures and the flow transported equally from the evaporator through each pipe into each condenser chamber. Thus, the present invention provides a solar evaporator which maximizes the sun's energy.
The present invention provides a new and improved solar evaporator. The solar evaporator of the present invention is utilized with thermal engines which have at least two heat pipes and a corresponding number of condenser chambers communicating with each heat pipe. The evaporator includes a parabolic dish shape disk for receiving reflected rays of the sun and constructed so as to include a pair of side-by-side chambers in heat exchange relation with the face which receives the solar heat. The chambers communicate with the heat pipes. Wicks adapted to transport the heating medium fluid are disposed within the chambers in engagement with the walls to transport fluid between the chambers and the heat pipes.
In one embodiment of the invention, an auxiliary body extends between the evaporator chambers and includes a wick structure in heat exchange relation with the wicks in the chambers so that the temperatures in the chambers are equalized even though the heat flux distribution on the face of the disk is uneven. If one chamber is hotter it heats the medium in the wick in the auxiliary body. The medium in the body in turn heats the medium in the chamber which was cooler, and this exchange continues until the chamber temperatures are substantially equal.
In a second embodiment of the invention, the chambers are separated by a common wall and wicks are arranged on opposite sides. When one chamber is hotter than the other the medium in the wick in that chamber that is engaged with the common wall will heat the corresponding medium in the other chamber. This process of heating and cooling as the distribution of solar heat flux on the receiving face of the disk continues to change continually equalizes the temperature in the chambers.
From the subsequent description and the appended claims taken in conjunction with the accompanying drawings, additional advantages and features of the present invention will become apparent to those skilled in the art.